The present invention relates to the radiography arts. It finds particular application in conjunction with computerized tomography (CT) scanners and will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other like applications requiring electrical signal transfer between a moving part and a stationary part.
Heretofore, CT scanners have commonly included a floor mounted frame assembly or gantry which remains stationary during an imaging procedure. A radiation generator, such as an x-ray tube, is mounted to a rotatable frame assembly or section which rotates around a patient being imaged. In third generation scanners, a radiation detector array is located within the rotating frame along with the x-ray tube. It is therefore necessary to provide a mechanism to transfer electrical signals to and from the rotating frame. That is, electrical power and control signals are transferred from the stationary frame to the rotating frame to power and control electronics, hardware, and the x-ray tube.
Additionally, a communications path is provided to transfer imaging data from the radiation detector array in the rotating frame to the stationary frame for image processing. The rotating gantry rotates rapidly, preferably one (1) revolution per second or less. The detector array includes numerous individual detectors, e.g. hundreds or even thousands. The detectors are sampled rapidly, typically in a fraction of a degree of rotation, to a high resolution, e.g. 32 bits or more. The amount of data to be transferred is so massive, that the data transfer rate is becoming a limiting factor in scanner speed and resolution.
Various devices are known for providing the communication path between the rotating frame and the stationary frame. Older CT scanners employed an umbilical cable. Typically, one or more flexible, shielded cables were hardwired to electronics such as the detector array, in the rotating frame. The cables were connected at the other end to stationary side electronics including image processing computers. Unfortunately the umbilical cable is typically capable of +/xe2x88x92360xc2x0 of rotation. Accordingly, the rotating frame on such umbilical devices is limited to a total of 720xc2x0 of rotation in one direction before the frame is stopped and rewound in the opposite direction.
Such xe2x80x9ccyclingxe2x80x9d type scanners were good for imaging a small number of slices. For larger volumes, continuous rotating scanners are preferred. The subject moves axially to create a spiral scanning pattern. In continuous rotate third generation systems, slip rings are commonly used to transfer power, data, and control signals. However, continuing improvements keep increasing rates of data transfer. On slip ring data links, the time required to propagate data signals around the circular rings effectively limits the maximum data transfer rate. Signals propagating around the ring in opposite directions may arrive at a reception point at offset times causing interference or garbled reception. Similar limitations are observed in slip ring data links employing capacitance-type data transfer.
Demands for higher data rates are increasingly being met, not through electrical slip ring configurations, but by optical data transmission links. Such data links typically employ a series of pulsating lights distributed around either the stationary frame or the rotating frame. On the opposing frame, an optical receiver is used to detect the synchronously strobing lights. The received light signals are then translated back into electronic image data for follow-on processing. Unfortunately, optical systems are more costly per channel of image data supplied, and greatly depend on the alignment of the optical transmitters and receivers. Moreover, optical systems are unusually sensitive to dirt and/or dust obscuring the optics.
Accordingly, a need exists for yet higher data transfer rates in CT type scanners which provide continuous rotation and reliable high-speed communications.
The present invention contemplates a new and improved method and apparatus for transferring electrical signals which overcomes the above-referenced problems and others.
In accordance with one aspect of the present invention, a computerized tomography system includes a stationary section defining a central opening and a concentric annular section positioned within the opening. At least one interconnecting data link provides communication between the stationary section and the rotating section. The interconnecting data link includes a plurality of receiving elements spaced angularly around the stationary section. On the rotating section, a plurality of transmitting elements are also angularly spaced. The transmitting elements are equal in number to, and in selective electrical communication with, the plurality of receiving elements.
In accordance with another aspect of the present invention, the plurality of receiving elements includes a ring configured as a plurality of electrically conductive segments separated by non-conductive interruptions.
In accordance with another aspect of the present invention, the transmitters include a number of brushes in selective physical contact with the conductive segments.
In accordance with another aspect of the present invention, the transmitters include capacitive couplers in selective electrical communication with the conductive segments.
In accordance with another aspect of the present invention, the tomography system includes an angular encoder which generates an angular displacement signal corresponding to a relative position of the rotating section within the stationary section. A de-multiplexer is also included which uses data including the angular displacement signal to arrange image data from the plurality of receiving elements into a desired format.
In accordance with another aspect of the present invention, the interconnecting data link further includes a second plurality of receiving elements axially spaced from the first set of receiving elements. On the rotating section, a second plurality of transmitting elements is likewise axially spaced from the first plurality of transmitting elements.
In accordance with another aspect of the present invention, the second plurality of receiving elements are angularly offset from the first plurality of receiving elements such that electrical communication between the stationary section and the rotating section is continuously provided.
In accordance with another embodiment of the present invention, a diagnostic imaging machine includes a rotating frame housing at least one array of radiation detectors selectively outputting imaging signals. A stationary frame is provided to support the rotating frame, and a plurality of simultaneous communication paths are provided for electrically transferring the imaging signals from the rotating frame to the stationary frame.
In accordance with another aspect of the present invention, the plurality of communication paths includes a ring configured as a plurality of electrically conductive segments separated by non-conductive interruptions. Further, a plurality of transmitting elements are in electrical communication with at least a portion of the radiation detectors, and in electrical communication with exactly one of the conductive segments when the rotating frame is at selected rotational angles.
In accordance with another aspect of the present invention, a rotational position sensor provides an angular displacement signal corresponding to the rotational angle of the rotating frame. A multi-channel decoder reorders data from each receiver into data channels based on the angular displacement signal provided.
In accordance with another aspect of the present invention, the imaging machine further includes at least a second slip ring parallel to the first slip ring also having a plurality of electrically conductive segments separated by non-conductive interruptions.
In accordance with another aspect of the present invention, the electrically conductive segments of the second slip ring are offset angularly from the segments of the first slip ring.
In accordance with another embodiment of the present invention, a radiographic process includes, while rotating an x-ray tube and an x-ray detector around an examination region, selectively activating the x-ray tube to direct radiation through the examination region onto the x-ray detector. Responsive to the radiation detected by the x-ray detector, channels of image data are generated. Selected ones of the image channels are then simultaneously electrically transmitted over a moving interface.
In accordance with another aspect of the present invention, following the transmitting, each of the selected plurality of data channels is arranged into a defined format.
In accordance with another aspect of the present invention, based on the detection of rotation, the transmitting is periodically interrupted.
One advantage of the present invention is that it improves data transfer efficiency.
Another advantage of the present invention resides in its simplicity.
Another advantage of the present invention resides in its extremely high data transfer rates.
Yet another advantage of the present invention resides in its space efficiency. Fewer slip ring assemblies can carry more data.
Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.